Logic built in self test circuitry for use in an integrated circuit with scan chains

ABSTRACT

Aspects include a system having logic built-in self-test (LBIST) circuitry for use in an integrated circuit with scan chains. The system includes a pattern generator configured for generating scan-in test values for said scan chains; a signature register configured for collecting scan-out responses from said scan chains after a clock sequence; an on-product control generator configured for controlling at least one test parameter; one or more microcode array or memory elements configured to receive inputs to initialize fields in the microcode array or memory elements; and a test controller. The test controller includes a reader component configured for reading test parameters from a field of the microcode array or the memory elements; and a programming component configured for configuring the on-product control generator and the pattern generator with a LBIST pattern according to the read test parameters.

BACKGROUND

The present invention generally relates to testing integrated circuitsand, more specifically, to logic built-in self-test circuitry for use inan integrated circuit with scan chains.

Digital integrated circuits are used for a diverse number of electronicapplications, from simple devices such as wristwatches to the mostcomplex computer systems. Defects in digital integrated circuits mayoccur.

“Stored patterns” was one of the first methods developed for testingdigital integrated devices for defects. According to the stored patternsmethod, a value per latch of the device under test (DUT) is defined, andthis data is stored in a chip tester and applied upon pattern execution.Similarly, a clock or capture sequence may be stored. After thefunctional clock sequence execution, the chip tester receives themeasured values per latch and compares them with the expected values todetermine defects in the DUT. The stored patterns method requires accessof the chip tester to each latch to be tested of the DUT. With millionsof latches on a chip this becomes a very time-consuming operation.

Logic built-in self-test (LBIST) has become a popular technique foron-chip testing of digital integrated circuits. LBIST offers a number ofbenefits targeted at the reduction of test time.

The scannable latches of the DUT may be broken into short scan chainsand the major components of LBIST circuitry include a pattern generator,a signature register and an on-product test control generator.

The pattern generator is initialized with a seed and provides scan-invalues to the scan chains. A clocking sequence is applied on the DUT andthe signature register collects scan-out responses from the scan chains.

The chip tester only needs to store an LBIST setup that includes heseed, the loop count, and the clock sequence. As the scan-in values aregenerated on the DUT at higher speeds compared to the testercommunication speed, the time necessary per loop is significantlyreduced.

As technology advances, the number of transistors on a chip increasesand the number of defects during manufacturing may increase, inparticular when a new manufacturing process is introduced. Moreover,said defects may be difficult to detect. Accordingly, more thoroughtesting may be required, which consumes more time and augments the testtime.

SUMMARY

Embodiments include a method, system, and computer program product forlogic built-in self-test circuitry for use in an integrated circuit withscan chains. A system includes a pattern generator configured forgenerating scan-in test values for said scan chains; a signatureregister configured for collecting scan-out responses from said scanchains after a clock sequence; an on-product control generatorconfigured for controlling at least one test parameter; one or moremicrocode array or memory elements configured to receive inputs toinitialize fields in the microcode array or memory elements; and a testcontroller. The test controller includes a reader component configuredfor reading test parameters from a field of the microcode array or thememory elements; and a programming component configured for configuringthe on-product control generator and the pattern generator with a LBISTpattern according to the read test parameters. The test parametersinclude one or more of number of loops, clock sequence, weight, seed,read/write the on-chip array, variables for the scan itself, andmasks/aperture.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 shows an integrated circuit that includes logic built-inself-test circuitry in accordance with some embodiments of thisdisclosure;

FIG. 2 is a flow chart illustrating a logic built-in self-test method inaccordance with some embodiments of this disclosure;

FIG. 3 is a flow chart illustrating another logic built-in self-testmethod in accordance with some embodiments of this disclosure;

FIG. 4 shows a further integrated circuit comprising logic built-inself-test circuitry and a chip tester in accordance with someembodiments of this disclosure; and

FIG. 5 is a flow chart illustrating an additional logic built-inself-test method in accordance with some embodiments of this disclosure.

DETAILED DESCRIPTION

Embodiments of the present invention may be better understood, and itsnumerous objects, features, and advantages made apparent to thoseskilled in the art by referencing the accompanying drawings.

The embodiment in FIG. 1 discloses an integrated circuit 101 comprisinglogic built-in self-test circuitry 102 and scan chains 103. The logicbuilt-in self-test circuitry 102 includes a pattern generator 104, asignature register 105 and an on-product control generation 106.

The pattern generator 104 is adapted to generate scan-in values for thescan chains 103 and the multi input register 105 to collect scan-outresponses from the scan chains 103. The on-product control generation106 provides the necessary control for steering the pattern generator104, the scan chains 103 and the signature register 105 as well asdriving the clock sequence to the functional logic.

Moreover, the logic built-in self-test circuitry includes a microcodearray 107 with inputs to initialize its fields. Test control means 108comprise reading means (not shown) to read test parameters from a fieldof the microcode array 107. Furthermore, the test control means 108include programming means (not shown) responsive to the reading means toconfigure the pattern generator 104 and the on-product controlgeneration 106 with the read test parameters.

The test parameters may include but is not limited to a seed, a type ofclock sequence, a number of loops, a scan clock rate and a weight.

Typically, the probability that a binary scan-in value generated by thepattern generator is “0” will be 1/2. Applying a weight to the patterngenerator may change the probability to 1/8, 7/8, 1/16, 15/16, 1/32,31/32, 1/64 or 63/64, respectively. This may enhance the chance todetect a defect in the DUT for certain circuits like a large OR or ANDgate.

Clocking sequence may include a launch-of clock and/or a launch-of scan.A launch-of clock may be used primarily to detect DC defects. Alaunch-of scan may be used primarily to detect AC defects. Furthermore,defects may only show up at a specific scan clock rate.

Performing several loops with the same weight, the same type of clocksequence and the same clock rate may increase test coverage at limitedadditional test time cost.

A set of test parameters to be applied to the DUT, i.e. the patterngenerator 104 and the on-product control generation 106, May also becalled an LBIST pattern.

From the fields of the microcode array 107 several different LBISTpatterns may be derived. The test control means may apply this LBISTpatterns on the DUT in the stored sequence or in a random order.

Each design of an integrated circuit may have its particular design fortest (DFT) requirements. The disclosed logic built-in self-testcircuitry may support executing LBIST patterns with different variationsin view of the particular DFT requirements.

The described logic built-in self-test circuitry has to be initializedonly once by the chip tester before performing the logic built-inself-test. In particular, only the fields of the microcode array 107have to be initialized. Thereafter, the different LBIST patterns may beexecuted automatically. Hence, considerable chip tester time may besaved compared to conventional logic built-in self-test circuitry, whereevery LBIST pattern has to be initialized separately by the chip tester.

For example, if the DFT requires three different clock sequences andfour different weights. The test control means 108 of the logic built-inself-test circuitry would sequence through and execute all twelvecombinations and weights with only one initialization of the logicbuilt-in self-test circuitry by initializing the fields of the microcodearray. Moreover, only one value from the signature register may berequired to determine, whether the logic built-in self-test circuitrypassed the test trough all said twelve LBIST patterns or if it failed.

A logic built-in self-test method like shown in FIG. 2 may be describedwith reference to FIG. 1. In a first step 201, the chip testerinitializes the logic built-in self-test circuitry with a setup for anumber of LBIST patterns. A first LBIST pattern is executed according tothe second step 202. After the execution step 202 it is determined,whether all LBIST patterns have been executed (step 203). If not, thenext LBIST pattern is executed pursuant to step 202. After all LBISTpatterns have been executed the final values in the signature registerare transmitted to the chip tester or readout by the chip tester forevaluation (step 204).

FIG. 3 shows another exemplary logic built-in self-test method. First,the chip tester initializes the fields of the microcode array andtransmits a starting signal to the logic built-in self-test circuitry(301). Thereafter, an LBIST pattern is read from fields of the microarray (302) and the on-product control generation and a patterngenerator is programmed according to the LBIST pattern (303). Afterrunning the LBIST pattern (304), collected scan-out responses from scanchains of the integrated circuit are compared with the expected data(305). If there is no agreement, the logic built-in self-test circuitryreports an error to the chip tester (306) and the logic built-inself-test is stopped (308). In case no error is detected, it isdetermined whether the executed LBIST pattern has been the last one(307). If true, the logic built-in self-test is stopped (308). If false,the next LBIST pattern is read from fields of the micro array (302).

FIG. 4 shows another integrated circuit 401 with scan chains 403 andlogic built-in self-test circuitry 402. The logic built-in self-testcircuitry 402 comprises a pattern generator 404, a signature register405 and an on-product control generation 406.

The pattern generator 404 may be configured for generating scan-invalues for the scan chains 403. The signature register 405 receives thescan-out responses from the scan chains 403. The on-product controlgeneration 406 controls the steering for driving the pattern generator404, the scan chains 403, and the signature register 405 as well asdriving the clock sequence to the functional logic.

Furthermore, the logic built-in self-test circuitry comprises amicrocode array 407 including inputs for initializing the fields of themicrocode array 407. Additionally, test control means 408 with readingmeans (not shown) and programming means (not shown) are provided. Thereading means are adapted to read test parameters from fields of themicrocode array 407 and the programming means are configured to programthe pattern generator 404 and the on-product control generation 406 withthe read test parameters. The test control means also include an LBISTmeasure register 409 for temporarily storing the LBIST measure values ofthe signature register 405 and a flag indicating that an LBIST patternhas been completely executed.

Moreover, a chip tester 410 is depicted in FIG. 4 in schematic form. Thechip tester 410 comprises a chip tester logic 411 and an expected testresult memory 412. The chip tester logic 411 may be adapted to start thelogic built-in self-test of the integrated circuit 401, i.e. the deviceunder test (DUT). The chip tester logic may determine whether the a flagin the LBIST measure register 409 has been set indicating that an LBISTpattern has been completely executed has been set and, depending on theresult, to download the LBIST measure values from the LBIST measureregister. The downloaded LBIST measure values may then be compared withthe expected LBIST values for the specific LBIST pattern, which arestored in the expected test result memory 412.

A still further logic built-in self-test method may be explained withreference to FIG. 5. As has been described hereinbefore, the methodstarts with initializing the fields of a microcode array of the logicbuilt-in self-test circuitry (501). Thereafter, a first LBIST pattern isexecuted (502), the LBIST measure values obtained by the signatureregister are transmitted into an LBIST measure register of the testcontrol means, and sets a flag in the LBIST measure register indicatingthat the LBIST pattern has been executed (503). Additionally,information indicative of the applied LBIST pattern (number of clocks,type of clock sequence, weight) may be stored in the LBIST measureregister. If it is determined in step 504 that the executed LBISTpattern was the last one, the logic built-in self-test is stopped (505).Otherwise, the steps 502 to 504 are repeated.

According to a first aspect, the invention relates to logic built-inself-test circuitry for use in an integrated circuit with scan chains,comprising (but not limited to) a pattern generator for generatingscan-in test values for said scan chains; a signature register forcollecting scan-out responses from said scan chains after a clocksequence; an on-product control generation to control at least one testparameter; a microcode array or memory element with inputs to initializeits fields; test control means comprising: reading means to read testparameters from a field of said microcode array, wherein the testparameters include at least one of a type of clock sequence, a number ofloops and a weight; programming means responsive to said reading meansto configure said on-product control generation and said patterngenerator with an LBIST pattern according to the read test parameters.According to a second aspect, the invention relates to a logic built-inself-test method comprising: initializing fields of a microcode array;reading test parameters from a field of the microcode array, wherein thetest parameters include at least one of a type of clock sequence, anumber of loops, a weight; programming a product control generation anda pattern generator with an LBIST pattern according to the read testparameters; generating scan-in values for scan chains with the patterngenerator; controlling at least one test parameter with the productcontrol generation; collecting scan-out responses from the scan chainsin a signature register.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiments were chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A system comprising logic built-in self-test(LBIST) circuitry for use in an integrated circuit with scan chains, thesystem comprising: a pattern generator configured for generating scan-intest values for said scan chains; a signature register configured forcollecting scan-out responses from said scan chains after a clocksequence; an on-product control generator configured for controlling atleast one test parameter; a communication component configured forcommunicating with a chip tester; a microcode array configured toreceive multiple sets of test parameters to initialize the microcodearray with a setup for a plurality of LBIST patterns, whereininitializing includes initializing, by the chip tester, fields of themicrocode array with the multiple sets of test parameters, wherein eachset of test parameters of the multiple sets of test parameters isassociated with a different LBIST pattern of the plurality of LBISTpatterns, and wherein the microcode array is initialized by the chiptester only once before the plurality of LBIST patterns are executed;and a test controller including: a reader component configured forreading test parameters associated with a first LIBIST pattern of theplurality of LBIST patterns from a field of the microcode array, whereinthe test parameters include one or more of number of loops, clocksequence, weight, seed, read/write the on-chip array, variables for thescan itself, and masks/aperture; and a programming component configuredfor configuring the on-product control generator and the patterngenerator with the first LBIST pattern according to the read testparameters.
 2. The system of claim 1, wherein the test controller isconfigured to repeatedly read test parameters associated with otherLIBST patterns of the plurality of LBIST patterns from fields of themicrocode array via the reader and to configure the on-product controlgenerator and the pattern generator with the other LBIST patternsaccording to the read test parameters sequentially.
 3. The system ofclaim 1, wherein the test controller is configured to repeatedly readtest parameters associated with other LIBST patterns of the plurality ofLBIST patterns from fields of the microcode array via the reader and toconfigure the on-product control generator and the pattern generatorwith the other LBIST patterns according to the read test parametersrandomly.
 4. The system of claim 1, wherein the communication componentfor communicating with the chip tester includes: a receiver configuredfor receiving a start request from the chip tester; a starter configuredfor, responsive to the receiver receiving the start request, triggeringthe test controller; and reporting component configured for, responsiveto the triggering the test controller, communicating test summary datato the chip tester.
 5. A method for logic built-in self-testing (LBIST),the method comprising: receiving multiple sets of test parameters at amicrocode array to initialize the array with a setup for a plurality ofLBIST patterns, wherein the initializing includes initializing, by achip tester, fields of the microcode array with multiple sets of testparameters, wherein each set of test parameters of the multiple sets oftest parameters is associated with a different LBIST pattern of theplurality of LBIST patterns, and wherein the microcode array isinitialized by the chip tester only once before executing the pluralityof LBIST patterns; reading test parameters associated with a firstLIBIST pattern of the plurality of LBIST patterns from a field of themicrocode array, wherein the test parameters include one or more of:number of loops, clock sequence, weight, seed, read/write the on-chiparray, variables for the scan itself, and masks/aperture; programming aproduct control generation and a pattern generator with the first LBISTpattern according to the read test parameters; executing the first LBISTpattern by generating scan-in test values for scan chains with thepattern generator and controlling at least one test parameter with theproduct control generation; and collecting scan-out responses from thescan chains in a signature register.
 6. The method of claim 5, furthercomprising repeatedly reading test parameters associated with otherLIBST patterns of the plurality of LBIST patterns from fields of themicrocode array and programming the product control generation and thegenerator with the other LBIST patterns in sequential order.
 7. Themethod of claim 5, further comprising: repeatedly reading testparameters associated with other LIBST patterns of the plurality ofLBIST patterns from fields of the microcode array and programming theproduct control generation and the generator with the other LBISTpatterns in random order.
 8. The method of claim 5, further comprising:receiving a start request from the chip tester; responsive to receivingthe start request, triggering the test controller; and responsive to thetriggering, communicating test summary data to the chip tester.
 9. Acomputer program product for logic built-in self-testing (LBIST),computer program product comprising a non-transitory computer readablestorage medium having program instructions embodied therewith, theprogram instructions executable by a processor to cause the processor toperform: receiving multiple sets of test parameters at a microcode arrayto initialize the microcode array with a setup for a plurality of LBISTpatterns, wherein the initializing includes initializing fields of themicrocode array with the multiple sets of test parameters, wherein eachset of test parameters of the multiple sets of test parameters isassociated with a different LBIST pattern of the plurality of LBISTpatterns, and wherein the microcode array is initialized only once bythe chip tester before executing the plurality of LBIST patterns;reading test parameters associated with a first LIBIST pattern from afield of the microcode array, wherein the test parameters include one ormore of: number of loops, clock sequence, weight, seed, read/write theon-chip array, variables for the scan itself, and masks/aperture;programming a product control generation and a pattern generator withthe first LBIST pattern according to the read test parameters; executingthe first LBIST pattern by generating scan-in test values for scanchains with the pattern generator and controlling at least one testparameter with the product control generation; and collecting scan-outresponses from the scan chains in a signature register.
 10. The computerprogram product of claim 9, wherein the program instructions furthercause the processor to perform: repeatedly reading test parametersassociated with other LIBST patterns of the plurality of LBIST patternsfrom fields of the microcode array and programming the product controlgeneration and the generator with the other LBIST patterns in sequentialorder.
 11. The computer program product of claim 9, wherein the programinstructions further cause the processor to perform: repeatedly readingtest parameters associated with other LIBST patterns of the plurality ofLBIST patterns from fields of the microcode array and programming theproduct control generation and the generator with the other LBISTpatterns in random order.
 12. The computer program product of claim 9,wherein the program instructions further cause the processor to perform:receiving a start request from the chip tester; responsive to receivingthe start request, triggering the test controller; and responsive to thetriggering, communicating test summary data to the chip tester.